The present disclosure relates to a sheet feeding device that feeds paper sheets. In addition, the present disclosure relates to an image forming apparatus including the sheet feeding device. In addition, the present disclosure relates to a method for controlling the sheet feeding device.
There are image forming apparatuses such as a multifunction peripheral, a copier, a printer, and a facsimile machine. The image forming apparatus stores paper sheets. For example, paper sheets are housed in a sheet cassette. When performing printing, the paper sheets are fed. The image forming apparatus (sheet feeding device) may perform detection about the paper sheets. There is a known example of a device that detects remaining quantity of paper sheets by using a sensor described below.
Specifically, there is a known sheet feed control device, which makes pressure contact with the top surface of paper sheets stacked on a sheet placing plate so as to feed a paper sheet, identifies stack quantity of paper sheets based on an induced voltage generated by an induction coil when the induction coil and electromagnetic field generation means are disposed at corresponding positions and one of them is disposed to move according to movement of the sheet placing plate, and determines presence or absence of a sheet feed cassette based on a detection signal output from a cassette detection unit.
The image forming apparatus includes the sheet feeding device. The sheet feeding device may include a sheet cassette. A bundle of paper sheets is set in the sheet cassette. To replenish or change paper sheets, the sheet cassette is detachable and attachable. When paper sheets run out, the sheet cassette is pulled out from the image forming apparatus. After paper sheets are replenished, the sheet cassette is inserted into the image forming apparatus.
During a period while the sheet cassette is detached, paper sheets cannot be fed. In other words, during a period while the sheet cassette is not attached, printing cannot be performed. Accordingly, a sensor for detecting whether or not the sheet cassette is attached is usually provided. In addition, if the sheet cassette is insufficiently inserted, sheet jamming may occur. Therefore, a contact-type switch is used as a sensor for detecting an attached or detached state. For example, a part of the contact-type switch contacts with a case of the sheet cassette. Using the contact-type sensor, it can be checked whether or not the sheet cassette is sufficiently inserted.
In addition, the sheet feeding device is equipped with a plurality of sensors other than the attachment/detachment detection sensor. For example, a sensor for detecting a sheet size and a sensor for detecting remaining quantity of paper sheets are disposed. As these sensors, a sensor including an actuator, and a plurality of optical sensors are used. One or more sensors are used for one detection item. There is a problem that an increase in the number of sensors causes an increase in development time and effort and in production cost.
In the known technique described above, one or more sensors are used for detecting remaining quantity of paper sheets. In addition, a cassette detection unit for detecting presence or absence of the sheet feed cassette is disposed separately. There is no description about a try to reduce the number of sensors, and hence the problem described above cannot be solved.